FR2761083A1 - New corrosion inhibitor compositions based on salts of mercapto acids and imidazoline(s) - Google Patents

Abstract

Corrosion inhibitor compositions for iron and ferrous metals in carbonated salt solutions comprise an active constituent based on an alkyl-poly(ethylamino)-imidazoline or 2-alkyl 3-(ethyl-amino)-1,3,diazoline of formula (I) and a mercaptoacid of formula R1-(R2CR3)-R4CR5-A (II). R = 10-22C hydrocarbyl(optionally unsaturated); n = 0-3; n = 0-3; R1 = H or SH ; R2 and R3 = 1 - 4C, CON(R6)(R7), COOR8; R4 and R5 = OH, NH2 or SH (when R1 is not SH); R6 and R7 = H, 1-4C; R8 = H, 1-8C; R2-R5 may be included in an aliphatic ring ; R3-R5 may be included in an aromatic ring when n = 1; and A = COOH, SO3H, OSO3H, PO3H or OPO3H. The molar ratio of the mercaptoacid component(s) to the imidazoline component(s) is between 1.0 to 1.5.Also claimed is a process for the inhibition of iron and ferrous metals using the new compositions as above

Description

DESCRIPTION

  The present invention relates to the inhibition of corrosion of iron and metals

  ferrous in carbonic brines.

  By carbon brines is meant in the sense of the invention, aqueous solutions of mineral salts loaded with carbon dioxide. Alkyl (C10-C22) -poly (ethyleneamino) -imidazolines, (or alkyl-2 poly (ethyleneamino) -3-diazolines-1,3) have long been recognized as excellent inhibitors of iron corrosion and ferrous metals in hydrogen sulfide, or hydrogen sulfide and carbonic brines, and many books have been devoted to the mechanism of this inhibition, to cite only the most recent, Preparation of Corrosion Inhibitor for Water Flooding in Oilfield and Study of its Mechanism , Lu Zhu et al., Water Treatments, 8 (1993), 253-264, China Ocean Press or Hydrogen Sulphide Corrosion of Steel, Mechanism of Action of Imidazoline Inhibitors, AJ Szyprowski,

  Proceedings of the 8th European Symposium on Corrosion Inhibitors, Ann. Univ.

  Ferrara, N.S., Sez. V, suppl. N. 10, 1995. But curiously, these compounds are very ineffective in corrosive media containing only C02, yet apparently less aggressive, which has motivated the search for more complex neighboring structures such as N, N 'substituted imidazolines ( US 5,322,640) or

  imidazolinone and urea adducts (GB 2,190,670).

  We have now found that the thioglycolates (mercaptoacetates) of alkyl-polyethyleneamino-imidazolines are very powerful corrosion inhibitors under these conditions. The invention thus consists in corrosion-inhibiting compositions comprising alkylpoly (ethyleneamino) -ididolines or 2-alkyl poly (ethyleneamino) -3-diazolines, corresponding to the general formula

H2 C CH2

  N - NCH2 CH2 [NH CH2InNH2 R in which R is a straight or branched, saturated or unsaturated hydrocarbon chain having from 10 to 22 carbon atoms, and o n is a number from 0 to

  3, and thioglycolic acid in a molar ratio of 1.0 to 1.5.

  These compositions, water-soluble like the traditional and ineffective imidazoline acetates, inhibit the static corrosion of iron and ferrous metals in carbonic brines with high salinity at high temperature, but also its dynamic corrosion under the conditions of production of gas. This efficiency is

  maintains in biphasic environments that are carbonic brines / oils.

  The alkylimidazolines used in the composition of the inhibitors of the invention are the condensation products with cyclization of fatty acids, saturated or unsaturated, with 10-22 carbon atoms, with polyethylene polyamines (diethylene triamine DETA and its higher counterparts, triethylene tetramine TETA, tetraethylene pentamine TEPA, pentaethylene hexamine PEHA). These imidazolines are obtained under conditions well known to those skilled in the art (introduction of the polyamine into the molten fatty acid, in the presence of oxalic acid

  acting as a cyclization accelerator, temperature rise up to 200 C -

  220 C and hold until the total condensation water has left).

  The inhibitors according to the invention are preferably presented in solution at -40% by weight in a water-miscible solvent, isobutanol, butylglycol, monoethylene glycol or their mixtures being preferred solvents. They are used at effective concentrations 5 to 200 ppm, preferably around 20 ppm of the preparation (calculated in volumes relative to the corrosive medium). Examples that

  follow will better understand the invention.

  EXAMPLE 1 Preparation of inhibitory compositions Various imidazolines are produced by condensing 1 mole of fatty acid with 1.15 mole of tetraethylenepentamine (TEPA) in the presence of 1% by weight of oxalic acid bihydrate. The amine is introduced into the fatty acid and oxalic acid mixture at the temperature of 140 ° C., after which the reaction mixture is brought to 160 ° C. and maintained at this temperature for 1 hour 30 minutes, then brought to between 200 ° C. and 220 ° C. for 16 hours. The inhibitor compositions consist of imidazolines (30% by weight), thioglycolic acid (5% by weight) and isobutanol (65% by weight). The corresponding controls consist of imidazolines, glacial acetic acid, and

  isobutanol in the same proportions.

  The inhibitory compositions 11, 12, 13 and 14 are thus produced, respectively, with imidazolines obtained from tall oil, coconut fatty acid, oleic fatty acid and rapeseed oil, and the control compositions (acetic) T1 to T4 corresponding.

  All these compositions are homogeneous liquids with an oily appearance.

EXAMPLE 2

  Static corrosion measurements are carried out in a medium consisting of an aqueous solution containing, in grams per liter: NaCl 277.50

KCI 6.43

  CaCI2, 2H20 21.50 MgCI2, 6H20 33.77 BaCI2, 2 H20 0.20 SrCI2, 2H20 0.34 FeCI2 0.06 This medium is previously deaerated with nitrogen, then saturated with CO2. Its pH is .5. The corrosion test is carried out on a 1 cm2 test piece of XC18 steel, in a device for measuring polarization resistance, the corrosive medium being at 80 ° C., the CO2 pressure being 1 bar. The results are reported in the table below, where they are expressed, as is traditional, as a percentage of protection.

PROTECTION PERCENTAGE

  Control formulas Formulas according to the invention (acetic) (thioglycolic) doses ppm T1 T2 T3 T4 I1l 13 13 14

1 -0 -0 -0 -0 -0 -0 8 8 7

7 -0 -0 0 -0 17 25 16 22

- 0 0 0 -0 64 60 71 69

- 0 -0 0 -0 81 82 83 86

- 0 - 0 0 - 0 84 89 85 87

- 0 -0 0 -0 85 90 84 90

- 0 - 0 - 0 - 0 86 92 83 92

18 0 - 0 0 86 94 88 94

  These results unequivocally reflect the effectiveness of the compositions

  imidazolines / thioglycolic acid according to the invention.

  EXAMPLE 3: dynamic corrosion test The test simulates gas production conditions. The corrosive medium consists of an aqueous NaCl solution at I g / l, deaerated beforehand with nitrogen, then saturated with CO2, brought to 60 ° C. and circulating at a speed of 13 meters per second in a device called "Jet" Impingement "(see: Correlation of Steel Corrosion in Pipe Flow with Jet Impingement and Rotating Cylinder Test, KD Efird et al., Corrosion, vol. 49, n 12, p. 992 - 1993). The test body subjected to corrosion under these conditions is a XC18 steel test piece in the form of a ring equal to 1 mm in width and with an internal radius equal to 2.5 mm, the measurement of which is

  corrosion rate by polarization resistance.

  FIG. 1 reproduces the results obtained from a blank test (without inhibitor) and in the presence of compositions T4 and 14 (respectively the formulations based on rapeseed imidazoline acetate and thioglycolate). The inhibitor compositions were used at a dose of 20 ppm (expressed in volumes of preparation relative to the corrosive medium). These results clearly demonstrate the effectiveness of the inhibitor according to the invention under the conditions of corrosion by carbonic brine.

  driven by a high flow speed.

  EXAMPLE 4 Corrosion test in a two-phase medium The corrosive medium is a mixed phase consisting of 90% by volume of an aqueous solution of sodium chloride at 1 g / l and 10% paraffinic oil. The system is deaerated beforehand by bubbling nitrogen, then saturated with CO2. The working temperature is 60 C. The homogeneity of the medium is ensured in the

  mounting using weak magnetic stirring.

  The corrosion inhibitor used is composition 14 (based on rapeseed imidazoline). It is used at a dose of 20 ppm (calculated as the volume of inhibitory preparation relative to the total volume of the corrosive medium). The corrosion rate is estimated as in the previous examples by polarization resistance, in

  a testing process summarized below.

  Conditions Corrosion rate in the aqueous phase (in mm / year) A. Precorrosion in the aqueous phase After precorrosion for 1.5 mm / year 12 hours B. Oil introduction After 2 hours of stabilization 1.4 mm / year C Introduction of the inhibitor via the oil phase After 12 hours of stabilization 0.002 mm / year

Claims (4)

  1. Composition inhibiting corrosion of iron and ferrous metals in carbonic brines comprising, as active ingredient, imidazoline thioglycolates, said imidazolines being 2-alkyl poly (ethyleneamino) -3 diazolines corresponding to the general formula H2C CH2 I I   N N CH2 CH2 [NH -CH2 CH2] nNH2 R in which R is a linear or branched, saturated or unsaturated hydrocarbon chain having from 10 to 22 carbon atoms, and o n is a number from 0 to 3. 2. Inhibitory compositions according to claim 1 comprising from 20 to 40% by weight of imidazoline thioglycolate in a water-soluble solvent, the ratio   molar between imidazoline and thioglycolic acid being 1.0 to 1.5.   3. Inhibitory compositions according to claim 2, wherein the solvent is isobutanol, butylglycol, monoethylene glycol or a mixture of these solvents. 4. Method for inhibiting corrosion of iron and ferrous metals in carbonic brines, in the presence or absence of oils, at rest or with a high flow rate, consisting in introducing into the corrosive medium from 5 to ppm compositions based on imidazoline thioglycolates of claims 1 to 3.